1. Field of the Invention
The present invention relates to an electromagnetic valve which includes a valve body for opening and closing a flow path of fluid.
2. Description of Related Art
In general, an electromagnetic valve (solenoid valve) is configured to have a coil, a fixed core and a movable core and generates a magnetic field by an electric current being caused to flow through the coil so as to attract the movable core towards the fixed core to thereby open and close the valve.
For example, an electromagnetic valve includes a funnel-shaped valve seat surface which is provided in an upper portion of a cylindrical valve seat element (a valve seat member) so as to be diametrically enlarged upwards, and a valve body having a semi-spherical distal end face is pressed against the valve seat surface so as to close a flow path in which fluid flows upwards from below (refer to FIG. 2 of JP-A-2004-360750)
Incidentally, in the electromagnetic valve, the action of the valve body largely influences a performance of the electromagnetic valve. For example, when the flow of fluid flowing towards the valve body is unstable, there emerges a situation where operation noise is generated by the valve body. In addition, there is a fear that the unstable movement of the valve body triggers a pulsation in fluid pressure in a hydraulic apparatus.
In the electromagnetic valve of JP-A-2004-360750, in view of these situations, the valve body takes a shape in which a tapered surface which is diametrically enlarged upwards extends continuously from the semi-spherical distal end face thereof. By taking the shape described above, it is expected that fluid, which flows upwards from below when the electromagnetic valve is opened, flow along the tapered surface of the valve body.
As is shown in FIG. 3A, however, when adopting a valve body configuration like the one disclosed in JP-A-2004-360750, since fluid which flows from an inlet path 62 below towards a valve body 5 is attracted towards both the valve body 5 and a valve seat surface 61, on one side (for example, a right-hand side in FIG. 3A), fluid flows along the valve body 5, and on the other side (for example, a left-hand side in FIG. 3A), there is a fear that fluid is separated from the valve body 5 to thereby be caused to flow along the valve seat surface 61.
In addition, also when adopting a valve body 5 as is shown in FIG. 3B in which a stem portion 52 is smoothly connected to a semi-spherical distal end (a seal portion 51), there is a fear that whether fluid flows along the valve body 5 or along a valve seat surface 61 becomes uncertain.
In valve bodies like those described above in which the flow of fluid tends to become uncertain, when actually assembled to electromagnetic valves, some operate properly and others do not. Due to this, there is a possibility that even with a minor production error or assembly error, an expected performance cannot be exhibited, and the performance of electromagnetic valves is caused to vary largely. Furthermore, the flow of fluid along the valve body 5 reaches as far as a portion of a return spring 81 for biasing the valve body 5, which is wound round a seat of the valve body 5, to thereby apply a force to the return spring 81. Thus, there is caused a problem that the controllability of the electromagnetic valve is worsened.